java泛型的使用，子类的泛型，可以通过父类来接收

    public static List<BaseEntity> getPageList(List<? extends  BaseEntity> childList){
        Integer pageNum = 0;
        Integer pageSize = 2;

        List<BaseEntity> baseList = new ArrayList<BaseEntity>();
        for(BaseEntity base : childList){
            baseList.add(base);
        }
        return baseList.subList(pageNum*pageSize,(pageNum+1)*pageSize);
    }